1. Field of the Invention
The present disclosure generally relates to an image forming apparatus including a recording head for jetting liquid droplet(s) and a sub-tank for supplying ink to the recording head.
2. Description of the Background Art
An image forming apparatus such as a printer, a facsimile machine, a copier, or a multi-functional device thereof may include a liquid jetting device including a recording head configured as, for example, a liquid jetting head for jetting liquid droplet(s) of a recording liquid (e.g., ink). Such image forming apparatuses jet liquid droplet(s) from nozzles of the liquid jetting head to form an image on a recording medium (hereinafter “sheet” or “sheets”).
Such image forming apparatuses can be categorized into two types. One type is a serial-type image forming apparatus, in which a recording head jets liquid droplet(s) while moving the recording head in a main scanning direction to form an image on a recording sheet. The other type is a line-type image forming apparatus, in which a line-type recording head extending in a width direction of a recording sheet jets liquid droplet(s) without moving the recording head to form an image.
In either case, such an image forming apparatus using a liquid jetting method includes a carriage including a sub-tank, and a main tank installed in a housing of the image forming apparatus. The sub-tank (or head tank, buffer tank) stores a relatively small amount of ink to be supplied to a recording head, and the main tank (or main cartridge, ink cartridge) stores a relatively large amount of ink to be supplied to the sub-tank. The main tank is connected to the sub-tank by a supply tube having some flexibility.
Conventionally, image forming apparatuses having an ink supply unit using such a sub-tank arrangement have been devised as below.
For example, JP-2006-240039-A discloses an image forming apparatus including a head carriage having a plurality of liquid sub-tanks, a plurality of liquid main tanks storing a plurality of recording inks, and a liquid supply unit for supplying liquid from the liquid main tank to the liquid sub-tanks. The plurality of liquid main tanks are provided and fixed in the image forming apparatus separately from the head carriage. The liquid supply unit and the plurality of liquid sub-tanks in the head carriage are connected by a plurality of liquid supply tubes. The liquid supply tubes are arranged and fixed together so that the liquid supply tubes form a sheet-like shape as a whole. The liquid supply tubes may be called a liquid supply tube band.
JP-2007-168403-A discloses another image forming apparatus including a head carriage and a carriage cover. The head carriage includes a joint unit to which a plurality of ink supply tubes, arranged in a horizontal direction, are connected. The head carriage is slidably supported on a plain face, which extends from the joint unit in the same direction in which the ink supply tubes are extending (e.g., horizontal direction). The carriage cover, provided at an upper part of the head carriage, includes a holding member for holding the ink supply tubes extending in the horizontal direction.
JP-2007-245349-A discloses yet another image forming apparatus including a recording head for jetting ink from nozzle(s) to record an image, an ink supply unit for supplying ink to the recording head, and a pressure member for applying pressure to the supply tubes, wherein the pressure member is pivotable.
JP-2006-205741-A discloses still another image forming apparatus including a plurality of ink tubes for supplying ink to a recording head, in which the ink tubes are arranged side-by-side and bundled together by an ink tube bundle member.
Although a plurality of supply tubes can be integrated in the sheet-like form, or can be integrated by the holding member, the bundle member, or the pressure member as above discussed, such configurations may become complex configurations. In view of such complexity, another configuration illustrated in FIG. 1 may be used, for example, in which a carriage 510 includes a tube fixing unit 512 having a groove 513. The groove 513 has a width D1 that is smaller than a tube diameter D of one supply tube (D1<D). A plurality of supply tubes 501a to 501e are arranged and fused together as an integrated supply tubes. Such integrated supply tubes can be called a supply tube band. The supply tubes 501a to 501e are fixed in the tube fixing unit 512 by pushing the supply tube band in the groove 513.
However, as illustrated in FIG. 2, when a plurality of supply tubes (e.g., five supply tubes) are arranged and fused side-by-side in a band-shape, for example, some supply tube(s) may be deviated from other supply tube(s) due to imprecise fusing. If such a deviation occurs, a width D2 of the supply tube band may become greater than the tube diameter D of one supply tube (D2>D). If such a supply tube band is pushed into the groove 513 of the tube fixing unit 512 as illustrated in FIG. 2, the deviated supply tube(s) may be get snagged or torn at a corner of the tube fixing unit 512, by which the supply tube(s) may be damaged because the groove 513 has a diameter corresponded to the tube diameter D of one supply tube.